Vasopressin

Vasopressin, also known as antidiuretic hormone (ADH), is a naturally occurring peptide hormone synthesized in the hypothalamus and released by the posterior pituitary gland. Its primary roles are to regulate the body's water balance by increasing water reabsorption in the kidneys (reducing urine output) and to constrict blood vessels, thereby increasing blood pressure. Vasopressin works by binding to V1 receptors on blood vessels (causing vasoconstriction) and V2 receptors in the kidneys (increasing water permeability in the collecting ducts). It is used clinically to treat diabetes insipidus (a condition of excessive thirst and urination due to ADH deficiency), to raise blood pressure in shock states, and to control bleeding in certain conditions. It also plays a role in social behavior, memory, and stress responses.